The throw appears fake, because it seems that uke is taking a fall for nage before uke is being touched.
In a full committed attack, an irimi technique can lead to a seriously ugly fall, or the ukemi may be difficult for that particular technique. Uke realizes this and trys to avoid a full irimi technique by going to the fall or ukemi before nage is able to unleash a full body force irimi. To the innocent bystander it appears that uke is falling on his own, and he is - but uke falls to avoid a powerful technique that is coming!
It should go without saying that this is probably more often done by a student who has been studying the art for a while. A newbie will probably unwittingly take the full force and quickly learn why you'd want to take a fall before the technique!